P-Type Barrier Dual-Band T2SL Infrared Detector
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Solution Overview
Problem
Dual-band photodetectors based on Type II Superlattice (T2SL) materials face limitations due to lattice mismatch and poor hole diffusion, leading to reduced quantum efficiency and high dark current, particularly in Long Wave InfraRed (LWIR) detectors.
Innovation Solution
A P-type doped barrier dual-band photodetector design with a Type II Superlattice barrier layer, eliminating the depletion region between absorber layers and minimizing minority carrier recombination, utilizing a structure with specific monolayer compositions and doping levels to enhance sensitivity and reduce dark current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Type II Superlattice (T2SL) materials are used for dual-band photodetectors, then sensitivity can be improved, but dark current increases due to poor hole diffusion and lattice mismatch
Solution Approach 1:
The patent applies parameter changes by transitioning from conventional p-n-p doping to p-B-p (p-type barrier-p-type absorber-p-type barrier) doping configuration. This changes the electrical parameters of the T2SL structure, creating flat-band conditions that suppress dark current while maintaining sensitivity. The specific doping levels and barrier thicknesses are optimized parameters that resolve the contradiction between sensitivity and dark current.
Solution Approach 2:
The patent implements equipotentiality by designing the p-B-p structure to maintain flat-band conditions across the absorber layers. This eliminates depletion regions and creates equipotential regions that prevent carrier accumulation and reduce generation-recombination currents, thereby suppressing dark current while preserving the detector's sensitivity to incident radiation.
2Ease of manufacture
If conventional p-N-p design is used, then manufacturing is simpler, but quantum efficiency is reduced due to depletion regions and electric fields
Solution Approach 1:
The patent applies inversion by reversing the conventional doping approach. Instead of using n-type barriers with p-type absorbers (p-n-p), it uses p-type barriers with p-type absorbers (p-B-p). This inverted approach eliminates the depletion regions and strong electric fields that plague conventional designs, thereby improving quantum efficiency while remaining manufacturable through standard epitaxial growth techniques.
3Speed
If T2SL absorber layers are doped n-type, then electron mobility is improved, but quantum efficiency is limited due to poor hole diffusion
Solution Approach 1:
The patent changes the doping parameter from n-type to p-type for both barriers and absorbers. This parameter change prioritizes hole transport over electron mobility, as the p-B-p structure creates favorable conditions for hole diffusion to the contacts while electrons are efficiently collected through the flat-band structure. This resolves the contradiction by optimizing for the dominant carrier type in the detection process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves suppressed dark current and improved quantum efficiency, allowing for low-bias operation and reduced generation-recombination current, effectively addressing the limitations of traditional p-N-p designs by maintaining a flat band condition and minimizing electric field in absorber layers.
Implementation Method 1
eliminating the depletion region between absorber layers and minimizing minority carrier recombination, utilizing a structure with specific monolayer compositions and doping levels to enhance sensitivity and reduce dark current
Implementation Method 2
dual-band photodetector comprising: a T2SL barrier layer with an upper surface and a lower surface, the T2SL barrier layer comprising a plurality of monolayers doped P type with a dopant; a first absorber layer disposed on the upper surface of the T2SL barrier layer; a second absorber layer disposed on the lower surface of the T2SL barrier layer
Data Source
AI summary
A dual-band infrared detector structure based on Type-II superlattices (T2SL) has been developed and experimentally validated. The structure according to the principles of the present invention is designed for a single Indium bump architecture and utilizes a T2SL barrier design that omits the traditional p-n junction region. The barrier design comprises multiple periods where each period comprises multiple monolayers doped P type. By selecting the composition, number of monolayers per period and number of periods, a transition region is created in the conduction band between a first absorber layer and a second absorber layer that allows operation at low biases (<100 mV for both bands) and exhibits a dark current density in the longer wavelength band comparable to that obtained with single-color detectors.